Power steering of an outboard motor can be carried out by means of a cable-activated power steering apparatus in which the outboard motor is connected though a linkage to the actuator housing of a hydraulic cylinder unit, and rotated about a vertical pivot axis by operation of the hydraulic cylinder unit. The hydraulic cylinder unit is supplied by a pump with hydraulic fluid under pressure, and the rate and direction of flow of the hydraulic fluid are controlled by valves inside the actuator housing, which are in turn operated by a valve actuator in the actuator housing and controlled remotely by a helm through a cable that slides longitudinally in a surrounding sheath. The cable is connected to one end of a steering rod (also commonly referred to as a “cable ram”) that is slidable in a tube mounted in fixed relation to a bracket by which the outboard motor is supported on a transom. The other end of the steering rod is connected to a lever on the actuator housing for controlling the valves.
The hydraulic cylinder unit operates as a “follow-up” mechanism, in which the movement of the actuator housing and cylinder ram follows the movement of the cable. Thus, in the case where the hydraulic cylinder unit is arranged so that the actuator housing and cylinder ram extend from the cylinder in the port direction, whenever the pilot rotates the helm clockwise to turn to starboard, the cable pushes the actuator lever and the actuator operates the valves in such a way as to extend the actuator housing and cylinder ram. On the other hand, whenever the pilot rotates the helm counterclockwise to turn to port, the cable pulls the actuator lever, and the actuator operates the valves in such a way as to retract the actuator housing and cylinder ram. Within a range of operation, the actuator housing and cylinder ram continue to move as long as the movement of the cable continues, and stop when movement of the cable stops and the lever on the actuator housing assumes a neutral position. The rate of movement of the actuator housing and cylinder ram is also dependent on the degree of opening of the valves, which is in turn dependent on the rate of movement of the cable as controlled by rotation of the helm.
An example of a cable-activated power steering apparatus is described in detail in U.S. Pat. No. 9,669,914, granted on Jun. 6, 2017. The entire disclosure of U.S. Pat. No. 9,669,914 is here incorporated by reference.
In most outboard-propelled boats, the outboard motor is supported on a transom that is a part of the boat's hull. The motor is mounted both for pivoting about a vertical axis for steering, and for tilting about a horizontal axis, not only for trim adjustment, but also so that the propeller can be raised to a level above the bottom of the hull for launching from, and landing on, a beach and for transport of the boat on a trailer. Most outboard engine mounts allow tilting through a range of 70° or more.
In the case of an outboard motor-propelled pontoon boat, the outboard motor is ordinarily supported on a “pod,” a structure located between the pontoons and supported from a deck extending from one pontoon to the other. A typical pod for mounting an outboard motor on a pontoon boat comprises a pair of laterally spaced side walls that diverge from each other, proceeding in the aft direction, and a transom extending from one side wall to the other at the aft ends thereof.
A typical power steering unit for a pontoon boat utilizes a hydraulic cylinder that moves on a rod extending between two mounting brackets. A link connected from the cylinder to a steering arm on the motor causes the motor to pivot about a substantially vertical steering axis as the hydraulic cylinder moves on the rod. When the engine is tilted, the cylinder and brackets move into a space between the side walls of the motor-supporting pod.
A cable-activated power steering apparatus can be utilized in a pontoon boat, but the spacing of the side walls of a motor-supporting pod is typically insufficient to permit tilting of the motor. A cable-actuated steering rod (i.e., a “cable ram”) is connected to a valve actuator on the actuator housing at the end of the cylinder ram. The steering rod typically extends through a “tilt tube” that is centered in relation to the motor and therefore also centered in relation to the pod. Because of the central location of the tilt tube, the steering rod moves through a range that extends past one of the side walls of pod. Consequently, the actuator housing at the outer end of the cylinder ram, which is connected to the end of the steering rod, will also extend past the side wall of the pod when the cylinder ram is fully extended. On tilting, if the cylinder ram is extended, the actuator housing can collide with a side wall of the pod. To remedy this problem, a common practice is to remove part of the side wall of the pod to provide clearance for the actuator housing and cylinder ram. However, removal of material degrades the strength of the pod.